I'd suggest don't panic, reasons of swollen ankles can be many
and one of them is obesity so...Forget about the ankles and concentrate on bringing your weight back to normal then you'll see what else will be needed, maybe not much. You cannot expect your body to function properly when is over weighted. There is no magic here, start eating healthy and be active physically. You're still young and you can be back on track in few months.
p.s.
I'd start with vegetables/fruits diet only for few months,
plus walking at least 1 hour a day.